Abstract The precision of various methods of
stellar photometry on old photographic plates is investigated using the
original plates or their digitized copies from the plate collection of the
Maria Mitchell Observatory (MMO). It is shown, in particular, that the simple
and fast method of eye photometry is comparable in precision to the traditional
“objective” methods using a microphotometer to measure the plates or image
analysis software to measure digital copies of small parts of the plates
obtained with a CCD camera. All these methods provide photometric accuracy of ±0.1–0.2 magnitude on the MMO plates. It is demonstrated
that the high-performance commercially available scanner AgfaScan T5000 used
for plate digitization at the MMO produces images that can be measured to a
considerably higher precision of ±0.05 magnitude, which is sufficient for most purposes of photographic
stellar photometry. The results of this investigation may be of interest to
those who use old plates for stellar photometry, as well as to those who look
for an adequate, fast, and relatively inexpensive scanner to digitize their
plate archive.